SEOUL, South Korea - North Korean leader Kim Jong Un had his defense chief executed with an anti-aircraft gun for complaining about the young ruler, talking back to him and sleeping during a meeting presided over by Kim, South Korea's spy agency told lawmakers Wednesday, citing what it called credible information.

South Korean analysts are split on whether the alleged bloody purge signals strength or weakness from Kim Jong Un, who took power after his father's 2011 death. Some aren't even sure whether Seoul's occasionally unreliable spy agency got it right. One expert described the reported development, part of a series of high-profile recent purges and executions by Kim, as an attempt to orchestrate a "reign of terror" that would solidify his leadership.

National Intelligence Service officials told a closed-door parliamentary committee meeting that North Korean People's Armed Forces Minister Hyon Yong Chol was killed in front of hundreds of spectators at a shooting range at Pyongyang's Kang Kon Military Academy in late April, according to lawmaker Shin Kyoung-min, who attended the briefing.

Kim Gwang-lim, chairman of the South Korean parliament's intelligence committee, quoted the spy service as saying Hyon had also failed several times to comply with unspecified instructions by the North Korean leader. The office of another lawmaker, Lee Cheol Woo, released similar information about the NIS briefing.

Also said to be purged was Ma Won Chun, a lieutenant general and prominent architect who reportedly led a megaproject to build North Korea's Masik Pass ski resort. Ma had frequently accompanied Kim Jong Un on inspection tours, but was last mentioned in state media in November. He was earlier appointed to lead a new "Designing Department" within the National Defense Commission, North Korea's top governing body.

The South Korean intelligence agency didn't tell lawmakers how it got its information, only that it was from a variety of channels and that it believed it to be true, the South Korean lawmakers said. The spy agency refused to confirm the report when contacted by The Associated Press.

After the briefing, Yonhap news agency cited an unidentified senior South Korean intelligence official as saying that Hyon's execution couldn't be completely confirmed yet because North Korea hadn't made an official announcement.

In Pyongyang, there were no announcements about any execution and no indications in tightly controlled state media about whether it was true or had taken place at all.

South Korea's spy agency has a spotty record of tracking developments in North Korea. Information about the secretive, authoritarian state is often impossible to confirm.

The spy service faced widespread criticism when it failed to predict the North's artillery strikes on a South Korean island in 2010 because it ignored intercepted North Korean communications that indicated a possible attack. The agency saved face in 2013 when it said Kim Jong Un had purged his powerful uncle, Jang Song Thaek, days before Pyongyang announced the former No. 2's execution because of alleged treason.

Unconfirmed sensational media reports have tended to follow past purges in the North.

Jang's execution saw a frenzy of media speculation, including wild reports that he was killed by a flame thrower or stripped naked and fed to hungry dogs. In 2012, media outlets followed the North's announcement that army chief Ri Yong Ho had stepped down because of an illness with reports that Ri may have been wounded or killed in a gun fight when soldiers loyal to him resisted an attempt to detain him. The NIS wasn't seen as being behind those reports.

Analyst Cheong Seong-chang at the private Sejong Institute think tank in South Korea questioned the authenticity of the report on Hyon's execution because the minister has not been edited out of state TV footage.

North Korea typically removes executed and purged officials from existing TV documentaries, but Hyon appeared multiple times in a TV documentary on live fire drills between April 30 and May 11, according to Seoul's Unification Ministry. North Korea's main news agency hasn't mentioned Hyon since an April 29 report of his attendance of a music performance the previous day.

Hyon was named the North's armed forces minister, the equivalent of South Korea's defense minister, in June of last year, and led a North Korean military delegation to a security conference in Moscow last month. He was made a vice marshal of the Korean People's Army in July 2012 before being demoted to a four-star general later that year, according to South Korea's Unification Ministry. Kim, the South Korean parliament's intelligence committee chief, said Hyon was the North Korean military's No. 2 after Hwang Pyong So, the top political officer at the Korean People's Army.

Kim Jong Un's purges are seen as efforts to bolster his grip on power. Last month, South Korean spy officials told lawmakers that North Korea executed 15 senior officials accused of challenging Kim's authority.

Koh Yu-hwan, a North Korea expert at Dongguk University in Seoul, said Kim Jong Un appears to be using purges to keep the military's old guard in check because they pose the only plausible threat to his rule. Koh said Kim could be pushing a "reign of terror" to solidify his leadership, but that those efforts would fail if he doesn't improve the country's shattered economy.